In the concrete construction industry mechanical bar splicing systems are widely employed. One such splicing system utilizing taper threaded bar ends and a matching taper thread coupler is sold by Erico Products, Inc. of Solon, Ohio, U.S.A. under the trademark LENTON. Tapered threads provide superior strength in the coupling. A standard or transition coupler, the latter connecting bars of different sizes, comprises simply internally taper threaded sleeves and are designed for connections where at least one bar can be turned on its axis.
In concrete construction there are many situations where neither bar is able to rotate either conveniently or not at all. Typical such situations are where one bar is bent, where bars are secured to each other, or where bar ends are projecting from already cast or precast concrete. Also in some situations where the bars are fixed and in clusters, the spacing between the taper threaded ends of bars to be joined may vary.
In such situations couplers known as position couplers are employed. Such couplers normally comprise separate threaded couplers for each bar end and a linking sleeve which engages the respective bar couplers. Such couplers may also be used with opposite hand threads to act as turnbuckles which when tightened draw the bar ends together. Examples of several forms of position couplers may be seen in U.S. Pat. No. 3,850,535.
A conventional position coupler such as that manufactured by Erico Products, Inc. of Solon, Ohio under such trademark LENTON includes a long female internally cylindrically threaded end member and a male externally cylindrically threaded connector end member, both of which are taper thread connected to the joined ends of reinforcing bar. A jam or lock nut is positioned on the threads of the male connector end and must be tightened against the female long end after the male and female ends are properly secured and tightened on the respective bars.
Position couplers, while quite adequate for the intended purpose, present some field installation problems. The male and female ends are of course rotated in the opposite directions for tightening and when the jam nut is tightened it is rotated on the cylindrical threads of the connector end in a direction which may tend to loosen the connector end taper threaded connection to its bar. Position couplers normally require torquing of at least some of the parts in opposite directions. If rotational slippage occurs, the connector end may require retightening and/or being held by a second wrench during the tightening of the jam nut. Since the field installation of such position couplers is not like working at a bench with a vise, a slippage problem can reduce the productivity of the installer.
In machined thread couplers, because of imperfect thread flank contact, when the coupling is placed under tension some axial slippage also may occur. Thus if flank contact can be improved when the coupling is formed, such axial slippage can be minimized.
Also, with prior position couplers, if the coupler is to be used as a connection socket abutting the form of a pour or in precast concrete, it is necessary to disassemble the coupler and cast in only the female portion of the coupler joined to a rod in the pour. In a pour there may be a considerable time lag after the pour before the form is removed and the complete connection is made. There is an even longer time period in precast construction between the casting and erection and assembly, wherein the coupling will be completed. Storing the remaining or male part of the coupling during such interval is a major problem particularly at a complex construction site. Anytime something has to be disassembled for use problems and delays can result. It would therefore be beneficial if the coupling and all its parts could be totally self-contained within a cylindrical sleeve so that disassembly of the parts would not be required.